Image sensing device

Abstract

The invention discloses an image sensing device. In one embodiment, an image sensing device may include: a substrate; a color filter that is formed over the substrate; first isolation regions formed on both sides of the color filter; and a microlens formed above the color filter, and a lower portion of the color filter may be formed in one region of an upper end of the substrate.

Description

Technical Field

[0001] Various embodiments of the disclosed technology relate to image sensing devices. Background Art

[0002] Image sensing devices refer to semiconductor devices that capture optical images and convert them into electrical signals. With the development of the automotive, medical, computer, and telecommunication industries, the demand for high-performance image sensing devices is increasing in various devices such as smartphones, digital cameras, gaming devices, the Internet of Things, robots, security cameras, and medical micro cameras.

[0003] Image sensing devices can be roughly divided into CCD (Charge Coupled Device) image sensing devices and CMOS (Complementary Metal Oxide Semiconductor) image sensing devices. Summary of the invention

[0004] The disclosed technology can be implemented in some embodiments to provide an image sensing device that can improve image quality by suppressing light induced pixel stain (LIPS).

[0005] In one embodiment, an image sensing device may include: a substrate; a color filter formed above the substrate; a first isolation region formed on both sides of the color filter; and a microlens formed above the color filter. In one example, a lower portion of the color filter may be formed in a region at an upper end of the substrate.

[0006] In one embodiment, an image sensing device may include: a substrate; a color filter including a lower portion and an upper portion, at least a portion of the lower portion is formed in an upper region of the substrate, and the upper portion is formed above the substrate; a first isolation region formed on both sides of the color filter; and a microlens formed above the color filter.

[0007] In one implementation, a boundary surface between the microlens and the color filter may be formed at a height between upper and lower ends of the first isolation region.

[0008] In one implementation, the second isolation region may be formed at both sides of the lower portion of the color filter.

[0009] In one implementation, a groove may be formed in one region of an upper end of the substrate, and a lower portion of the color filter may be formed in the groove.

[0010] In one embodiment, at least a portion of a lower portion of the color filter is disposed in a groove formed in an upper region of the substrate.

[0011] In one implementation, an isolation layer may be formed under the color filter.

[0012] In one implementation, the first isolation region may include a barrier metal layer formed over the isolation layer and a metal layer formed over the barrier metal layer.

[0013] In one implementation, a boundary surface between the microlens and the color filter may be formed at a height between upper and lower ends of the metal layer.

[0014] In one embodiment, an image sensing device may include: a substrate; a color filter formed above the substrate; a microlens formed above the color filter; and a photodiode located in the substrate, and a first isolation region may be formed on both sides of an upper portion of the color filter and a second isolation region may be formed on both sides of a lower portion of the color filter.

[0015] In one embodiment, an image sensing device may include: a substrate; a color filter including a lower portion and an upper portion, at least a portion of the lower portion is formed in an upper region of the substrate, and the upper portion is formed above the substrate; a microlens formed above the color filter; a photodiode formed in the substrate; a first isolation region formed on both sides of the upper portion of the color filter; and a second isolation region formed on both sides of the lower portion of the color filter.

[0016] In one implementation, at least a portion of a lower portion of the color filter may be formed in an upper region of the substrate.

[0017] In one embodiment, a lower portion of the color filter may be formed over the photodiode.

[0018] In one implementation, a boundary surface between the microlens and the color filter may be formed at a height between upper and lower ends of the first isolation region.

[0019] In one embodiment, at least a portion of a lower portion of the color filter is disposed in a groove formed in an upper region of the substrate.

[0020] In one implementation, an isolation layer may be formed under the color filter.

[0021] In one implementation, the first isolation region may include a barrier metal layer formed over the isolation layer and a metal layer formed over the barrier metal layer.

[0022] In one implementation, a boundary surface between the microlens and the color filter may be formed at a height between upper and lower ends of the metal layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a block diagram of an image sensing device according to one embodiment.

[0024] Figure 2 and Figure 3 An example structure of an image sensing device according to one embodiment is shown. DETAILED DESCRIPTION

[0025] Features and certain advantages related to specific implementations of the disclosed technology disclosed in this patent document are described by way of example embodiments with reference to the accompanying drawings.

[0026] When incident light passing through a microlens is collected, a focus is formed at the location of the color filter, thereby generating spots called "voids" on the color filter, which leads to image quality degradation. The disclosed technology can be implemented in some embodiments to solve these problems by providing an image sensing device capable of preventing light-induced pixel staining (LIPS).

[0027] In some implementations, since the upper region of the color filter is formed between the isolation regions on both sides and the lower region of the color filter is formed in one region of the substrate, a focus is formed in the lower portion of the microlens, thereby preventing light induced pixel stains (LIPS) or image quality defects.

[0028] Figure 1 is a block diagram of an image sensing device according to one embodiment.

[0029] Reference Figure 1 , an image sensing device according to one embodiment may include a pixel array 1100, a row driver 1200, a correlated double sampler (CDS) 1300, an analog-to-digital converter (ADC) 1400, an output buffer 1500, a column driver 1600, a timing controller 1700, and a bias generator 1800. The components of the illustrated image sensing device are discussed only by way of example, and this patent document covers addition or omission of components when necessary.

[0030] The pixel array 1100 may include a plurality of pixels arranged in a plurality of rows and columns. In one embodiment, the plurality of pixels may be arranged into a two-dimensional pixel array including rows and columns. In another example, a plurality of unit imaging pixels may be arranged into a three-dimensional pixel array. A plurality of pixels may convert an optical signal into an electrical signal based on a unit pixel or based on a pixel group, and the pixels in the pixel group share at least some internal circuits. The pixel array 1100 may receive a drive signal including a row selection signal, a pixel reset signal, and a transfer signal from a row driver 1200. Upon receiving the drive signal, the corresponding pixel in the pixel array 1100 may be activated to perform operations corresponding to the row selection signal, the pixel reset signal, and the transfer signal.

[0031] The row driver 1200 may activate the pixel array 1100 based on the command and control signal provided by the timing controller 1700 to perform certain operations on the pixels in the corresponding row. In one embodiment, the row driver 1200 may select at least one pixel arranged in at least one row of the pixel array 1100. The row driver 1200 may generate a row selection signal to select at least one row among a plurality of rows. The row driver 1200 may sequentially enable a pixel reset signal and a transfer signal for pixels corresponding to at least one selected row. Therefore, a reference signal and an image signal as an analog signal generated by each pixel of the selected row may be sequentially transferred to the CDS 1300. At this time, the reference signal may be an electrical signal provided to the CDS 1300 when the sensing node (e.g., a floating diffusion node) of the pixel is reset, and the image signal may be an electrical signal provided to the CDS 1300 when the photocharge generated by the pixel is accumulated in the sensing node. The reference signal representing the reset noise inherent in the pixel and the image signal representing the incident light intensity may be collectively referred to as a pixel signal.

[0032] CMOS image sensors can use correlated double sampling (CDS) to remove the difference between the two samples by sampling the pixel signal twice, thereby removing undesirable pixel offset values ​​known as fixed pattern noise. In some embodiments, correlated double sampling (CDS) can remove undesirable offset values ​​of pixels by comparing the pixel output voltages obtained before and after the photocharges generated by the incident light are accumulated in the sensing node, so that only the pixel output voltage based on the incident light can be measured. In one embodiment, CDS1300 can sequentially sample and hold reference signals and image signals provided from the pixel array 1100 to each of the multiple column lines. That is, CDS1300 can sample and hold reference signals and image signals corresponding to each column of the pixel array 1100.

[0033] The CDS 1300 may transmit the reference signal and the image signal of each column as a correlated double sampling signal to the ADC 1400 based on a control signal from the timing controller 1700 .

[0034] ADC 1400 is used to convert the CDS signal into a digital signal for each column and output the digital signal. In one embodiment, ADC 1400 can be implemented as a ramp comparison ADC. The ramp comparison ADC may include a comparator circuit for comparing an analog pixel signal with a ramp signal that ramps up or down over time and a counter that counts until the ramp signal matches the analog pixel signal. In one embodiment, ADC 1400 can convert the correlated double sampling signal generated by CDS 1300 for each column into a digital signal and output the digital signal.

[0035] The ADC 1400 may include a plurality of column counters corresponding to each column of the pixel array 1100. Each column of the pixel array 1100 is coupled to the column counter, and image data may be generated by converting a correlated double sampling signal corresponding to each column into a digital signal using the column counter. In another embodiment, the ADC 1400 may include a global counter to convert a correlated double sampling signal corresponding to each column into a digital signal using a global code provided from the global counter.

[0036] The output buffer 1500 may temporarily hold the column-based image data provided from the ADC 1400 to output the image data. The output buffer 1500 may temporarily store the image data output from the ADC 1400 based on a control signal of the timing controller 1700. The output buffer 1500 may be used as an interface to compensate for a data rate difference or a transfer (or processing) rate difference between the image sensing device and other devices.

[0037] The column driver 1600 may select a column of the output buffer 1500 based on a control signal from the timing controller 1700, and sequentially output image data temporarily stored in the selected column of the output buffer 1500. In one embodiment, upon receiving an address signal from the timing controller 1700, the column driver 1600 may generate a column selection signal based on the address signal and select a column of the output buffer 1500, outputting the image data from the selected column in the output buffer 1500 as an output signal.

[0038] The timing controller 1700 may control at least one of the row driver 1200 , the CDS 1300 , the ADC 1400 , the output buffer 1500 , the column driver 1600 , and the bias generator 1800 .

[0039] The timing controller 1700 may provide clock signals required for operations of the respective components of the image sensing device, control signals for timing control, and address signals for selecting rows or columns, signals for controlling the level of bias voltage applied to the pixel array 1100, etc. to at least one of the row driver 1200, the CDS 1300, the ADC 1400, the output buffer 1500, the column driver 1600, and the bias generator 1800. In one embodiment of the disclosed technology, the timing controller 1700 may include a logic control circuit, a phase-locked loop (PLL) circuit, a timing control circuit, a communication interface circuit, etc.

[0040] The bias generator 1800 may generate a bias voltage for suppressing a dark current generated in pixels of the pixel array 1100 and supply the generated bias voltage to the pixel array 1100 .

[0041] The bias voltage may be determined during wafer probe testing of the image sensing device and stored in a one-time programmable (OTP) memory. For example, the bias voltage may be determined experimentally to be a value that maximizes the dark current suppression effect while minimizing unnecessary power consumption without compromising the performance of the image sensing device.

[0042] The bias generator 1800 may generate a voltage corresponding to a bias voltage stored in the OTP memory. In one embodiment, the OTP memory may be included in the image sensing device, and in particular, may be included in the bias generator 1800.

[0043] In one embodiment, the bias voltage may have a plurality of values. In one example, the bias voltage may have one of the plurality of values ​​at a specific timing.

[0044] In some implementations, the plurality of values ​​may correspond to a plurality of operating modes of the image sensing device, respectively. The dark current generated at a low brightness level and the dark current generated at a high brightness level may be different from each other, and in order to effectively suppress the dark current in each environment by the bias generator 1800, the bias voltage may vary according to the mode.

[0045] In some implementations, the multiple values ​​may respectively correspond to multiple regions of the pixel array 1100. Dark currents generated at different positions of pixels in the pixel array 1100 may be different from each other, and in order for the bias generator 1800 to effectively suppress the dark current regardless of the position of the pixel, the bias voltage may vary depending on the region.

[0046] In one example, the bias voltage may be a negative voltage having a negative sign, but the disclosed technology is not limited thereto.

[0047] Figure 2 and Figure 3 is a view for describing the structure of an image sensing device according to one embodiment.

[0048] Reference Figure 1 and Figure 2 , the pixel array 1100 according to one embodiment may include a plurality of unit pixels 100 .

[0049] The unit pixel 100 may include a substrate 110, a color filter 120, a microlens 130, an optical detector 140, a first isolation region 150, a second isolation region 160, and an isolation layer 170. The microlens 130 and the color filter 120 are positioned above the optical detector 140 to guide incident light to the optical detector 140 through the microlens 130 and the color filter 120, so that only light of a specific color filtered by the color filter 120 enters the optical detector 140. The optical detector 140 operates to convert the received filtered light into an optical detector signal as a pixel signal of the unit pixel 100, and in some implementations, the optical detector 140 may include, for example, a photodiode.

[0050] In one implementation, the substrate 110 may include a silicon (Si) material in a single crystal state.

[0051] In one embodiment, the color filter 120 may be formed over the substrate 110 to filter and pass visible light from among the light incident on the color filter 120 via the microlens 130. In one embodiment, the color filter 120 may include one of a blue filter, a green filter, and a red filter. Here, the blue filter passes blue light and blocks visible light of other wavelengths, the green filter passes green light and blocks visible light of other wavelengths, and the red filter passes red light and blocks visible light of other wavelengths.

[0052] In some embodiments of the disclosed technology, the color filter 120 may include an upper portion A and a lower portion B.

[0053] In one implementation, at least a portion of the lower portion B of the color filter 120 may be formed in an upper region (eg, an upper end) of the substrate 110. In one example, as Figure 3 As shown, a lower portion of the lower portion B of the color filter 120 may be formed in an upper portion of the substrate 110 .

[0054] In one embodiment, the groove 111 is formed in the upper region of the substrate 110. In one example, the groove 111 is formed by etching the upper region of the substrate 110. In one embodiment, the lower portion B of the color filter 120 may be formed in the groove 111 of the substrate 110. The lower portion B of the color filter 120 may be formed in the groove 111 in the upper region of the substrate 110.

[0055] In one implementation, a lower portion B of the color filter 120 may be formed above the optical detector 140 .

[0056] In one implementation, the upper portion A of the color filter 120 may be formed between the first isolation regions 150. In one example, the first isolation region 150 is formed to protrude from an upper surface of the color filter 120 toward the microlens 130 disposed above the color filter 120.

[0057] In one implementation, a boundary surface C between the microlens 130 and the color filter 120 may be formed between the upper and lower ends of the first isolation region 150 .

[0058] In one implementation, the lower portion B of the color filter 120 may be formed between the second isolation regions 160 .

[0059] In some embodiments, the depth of the upper portion A of the color filter 120 is the same as the depth of the lower portion B of the color filter 120. In some embodiments, the depth of the upper portion A of the color filter 120 is different from the depth of the lower portion B of the color filter 120. In one example, the depth of the lower portion B of the color filter 120 is deeper than the depth of the upper portion A of the color filter 120. In another example, the depth of the upper portion A of the color filter 120 is deeper than the depth of the lower portion B of the color filter 120.

[0060] Since the boundary surface C serving as the boundary between the microlens 130 and the color filter 120 is formed at a height between the upper and lower ends of the first isolation region 150, and the lower portion B of the color filter 120 is formed in the upper region of the substrate 110, a focus can be formed in the lower portion of the microlens 130 rather than in the color filter 120, thereby preventing spots referred to as “gaps” from being generated in the color filter 120.

[0061] The microlens 130 may be formed above the color filter 120 , and may serve to collect light incident on the microlens 130 from the outside.

[0062] The optical detector 140 may be formed in an inner region of the substrate 110, and an n-type impurity region and a p-type impurity region may be vertically stacked in the optical detector 140. The n-type impurity region and the p-type impurity region may be formed through an ion implantation process.

[0063] The first isolation region 150 may be formed at both sides of the upper portion A of the color filter 120 .

[0064] In one implementation, the first isolation region 150 may include a barrier metal layer 151 and a metal layer 152 .

[0065] In one implementation, the barrier metal layer 151 may be formed over the isolation layer 170 and may include a titanium nitride (TiN) layer.

[0066] In one implementation, the metal layer 152 may be formed over the barrier metal layer 151 and may include tungsten (W).

[0067] In one implementation, a boundary surface C between the microlens 130 and the color filter 120 may be formed between the upper and lower ends of the metal layer 152 .

[0068] In one implementation, the first isolation region 150 may include an air layer (not illustrated).

[0069] In one implementation, the second isolation region 160 may be formed on both sides of the lower portion B of the color filter 120 .

[0070] The second isolation region 160 may be formed in a vertical deep groove to prevent crosstalk between adjacent sub-pixels 200 , and may be formed by a deep trench isolation (DTI) process.

[0071] The second isolation region 160 may include at least one of a silicon oxynitride (SiON) layer, a silicon oxide (SiO) layer, or a silicon nitride (SiN) layer.

[0072] The second isolation region 160 may be formed on both sides of the optical detector 140 .

[0073] The second isolation region 160 may be formed at both sides of the lower portion B of the color filter 120 .

[0074] An isolation layer 170 may be formed under the color filter 120 .

[0075] In one implementation, the isolation layer 170 may include at least one of an oxide layer, a nitride layer, or an oxynitride layer.

[0076] In some embodiments of the disclosed technology, since the boundary surface C between the microlens 130 and the color filter 120 is formed at a height between the upper end and the lower end of the first isolation region 150, and the lower portion B of the color filter 120 is formed in the region of the upper end of the substrate 110, a focus can be formed in the lower portion of the microlens 130 instead of in the color filter 120, thereby preventing spots called “gaps” in the color filter 120.

[0077] In addition, an upper region of the color filter is formed between isolation regions provided on both sides, and a lower portion of the color filter is formed in a region at an upper end of the substrate, and accordingly, a focus is formed in a lower portion of the microlens rather than in the color filter, thereby preventing image quality degradation associated with light induced pixel stain (LIPS).

[0078] Although this patent document contains many details, these details should not be interpreted as limitations on the scope of any subject matter or the content claimed, but as descriptions of features of specific embodiments that may be specific to a particular technology. Certain features described in the context of separate embodiments in this patent document may also be implemented in combination in a single embodiment. On the contrary, the various features described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable sub-combination. In addition, although features may be described above as working in certain combinations and even initially claimed as such, in some cases, one or more features from the claimed combination may be removed from the combination, and the claimed combination may involve a sub-combination or a variation of the sub-combination.

[0079] Only a few implementations and examples of the disclosed technology are described, and other implementations, enhancements, and variations may be made based on what is described and illustrated in this patent document.

[0080] CROSS-REFERENCE TO RELATED APPLICATIONS

[0081] This patent document claims priority to and the benefit of Korean Patent Application No. 10-2023-0160644, filed on November 20, 2023, which is incorporated herein by reference in its entirety as a part of the disclosure of this patent document.

Claims

1. An image sensing device, comprising: substrate; a color filter formed above the substrate; a first isolation region formed on both sides of the color filter; as well as a microlens formed above the color filter, Wherein, a lower portion of the color filter is formed in an upper region of the substrate.

2. The image sensing device according to claim 1, in, A boundary surface between the microlens and the color filter is formed at a height between upper and lower ends of the first isolation region.

3. The image sensing device according to claim 1, further comprising: A second isolation region is formed at both sides of the lower portion of the color filter.

4. The image sensing device according to claim 1, in, At least a portion of the lower portion of the color filter is disposed in a groove formed in the upper region of the substrate.

5. The image sensing device according to claim 1, further comprising: An isolation layer is formed under the color filter.

6. The image sensing device according to claim 5, in, The first isolation area includes: a barrier metal layer formed over the isolation layer; and A metal layer is formed over the barrier metal layer.

7. The image sensing device according to claim 6, in, A boundary surface between the microlens and the color filter is formed at a height between an upper end and a lower end of the metal layer.

8. An image sensing device, comprising: substrate; a color filter formed above the substrate; a microlens formed above the color filter; a photodiode formed in the substrate; a first isolation region formed on both sides of an upper portion of the color filter; as well as A second isolation region is formed at both sides of a lower portion of the color filter.

9. The image sensing device according to claim 8, in, At least a portion of the lower portion of the color filter is formed in an upper region of the substrate.

10. The image sensing device according to claim 9, in, The lower portion of the color filter is formed over the photodiode.

11. The image sensing device according to claim 9, in, A boundary surface between the microlens and the color filter is formed at a height between upper and lower ends of the first isolation region.

12. The image sensing device according to claim 9, in, At least a portion of the lower portion of the color filter is disposed in a groove formed in the upper region of the substrate.

13. The image sensing device according to claim 9, further comprising: An isolation layer is formed under the color filter.

14. The image sensing device according to claim 13, in, The first isolation area includes: a barrier metal layer formed over the isolation layer; and A metal layer is formed over the barrier metal layer.

15. The image sensing device according to claim 14, in, A boundary surface between the microlens and the color filter is formed at a height between an upper end and a lower end of the metal layer.

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